1. Field of the Invention
This invention relates to a catalyst composition useful in the hydroprocessing of a sulfur- and metal-containing hydrocarbon feedstock, and to a method for the catalytic hydroprocessing of a sulfur- and metal-containing hydrocarbon feedstock employing such a catalyst composition. More particularly, this invention relates to a catalyst composition comprising a specified amount of an oxide of nickel or cobalt and a specified amount of an oxide of molybdenum, the catalyst further characterized by having a specified pore size distribution, a specified molybdenum gradient from the interior to the exterior of a given catalyst pellet and a specified percentage of the nickel or cobalt in acid extractable form. This invention also relates to a method for hydroprocessing a sulfur- and metal-containing hydrocarbon feedstock which comprises contacting the feedstock with hydrogen and the abovedescribed catalyst in such a manner that the catalyst is maintained at isothermal conditions and is exposed to a uniform quality of feed.
2. Information Disclosure Statement
Co-assigned U. S. Pat. application Ser. No. 168,095, filed Mar. 14, 1988 now U.S. Pat. No. 4,941,964, incorporated herein by reference, discloses a process for the hydrotreatment of a sulfur and metal-containing hydrocarbon feed which comprises contacting the feed with hydrogen and a catalyst in a manner such that the catalyst is maintained at isothermal conditions and is exposed to a uniform quality of feed. The catalyst has a composition comprising 3.0-5.0 wt. % of an oxide of a Group VIII metal, 14.5-24.0 wt. % of an oxide of a Group VIB metal and 0-2.0 wt. % of an oxide of phosphorus supported on a porous alumina support, and the catalyst is further characterized by having a total surface area of 150-210 m.sup.2 /g and a total pore volume (TPV) of 0.50-0.75 cc/g with a pore diameter distribution such that micropores having diameters of 100-160A constitute 70-85% of the total pore volume of the catalyst and macropores having diameters of greater than 250A constitute 5.5-22.0% of the total pore volume of the catalyst.
U.S. Pat. No. 4,670,132 (Arias et al.) discloses a catalyst preparation and a catalyst composition useful in the hydroconversion of heavy oils, the catalyst comprising a high iron content bauxite with the addition of one or more of the following promoters: phosphorus, molybdenum, cobalt, nickel or tungsten. The bauxite catalysts typically contain 25-35 wt% aluminum. The catalysts have certain characteristic features for the elemental components (including aluminum and where present, molybdenum) when the pellet exteriors are examined in the fresh oxide state using X-ray photoelectron spectroscopy (XPS). For those catalysts which contain molybdenum, the surface Mo/Al atomic ratios on the pellet exteriors are in the range of 0.03 to 0.09. Arias is distinguished from the instant invention in that its catalyst requires a bauxite support whereas the catalyst of the instant invention does not. In addition, Arias requires a surface Mo/Al atomic ratio on the pellet exteriors in the range of 0.03 to 0.09 when the fresh oxide catalyst is examined by XPS whereas the catalysts of the instant invention are characterized by: (1) bulk Mo/A1 atomic ratios of 0.06-0.075 as measured by traditional techniques; (2) surface Mo/Al atomic ratios on the pellet exteriors of 0.20-0.55 as measured by XPS on the fresh oxide catalysts; (3) surface Mo/A1 atomic ratios on the crushed catalyst pellets of 0.10-0.15 as measured by XPS on the fresh crushed oxide catalysts, and, (4) that the ratio of the surface Mo/A1 atomic ratios of the pellet exteriors relative to the surface Mo/A1 atomic ratios of the crushed catalyst pellets be less than 6.0.
U.S. Pat. No. 4,652,545 (Lindsley et al.), incorporated herein by reference, discloses a catalyst composition useful in the hydroconversion of heavy oils, the catalyst containing 0.5-5% Ni or Co and 1.8-18% Mo (calculated as the oxides) on a porous alumina support, having 15-30% of the Ni or Co in an acid extractable form, and further characterized by having a TPV of 0.5-1.5 cc/g with a pore diameter distribution such that (i) at least 70% TPV is in pores having 80-120A diameters, (ii) less than 0.03 cc/g of TPV (6% TPV) is in pores having diameters of less than 80A, and (iii) 0.05-0.1 cc/g of TPV (3-20% TPV) is in pores having diameters of greater than 120A. Lindsley et al. is distinguished from the instant invention in that although it teaches that having a proportion of nickel or cobalt contained in its catalyst in an acid extractable form is advantageous in terms of heavy oil hydroconversion, Lindsley et al. does not teach or suggest that catalysts which have a prescribed molybdenum gradient are advantageous in terms of heavy oil hydroconversion.
U.S. Pat. No. 4,588,709 (Morales et al.) discloses a catalyst preparation and a catalyst composition useful in the hydroconversion of heavy oils, the catalyst comprising 5-30 wt% of a Group VIB element (e.g. molybdenum) and 1-5 wt% of a Group VIII element (e.g. nickel). Morales et al. indicate that the finished catalysts have average pore diameters of 150 to 300 Angstroms. The catalysts have certain characteristic features for the active components (Mo and Ni) when the pellet exteriors are examined in a sulfided state using X-ray photoelectron spectroscopy (XPS). Morales (`709) is distinguished from the instant invention in that its catalyst requires a large average pore diameter (150 to 300 Angstroms) whereas the catalyst of the instant invention has median pore diameters of 120 to 130 Angstroms. In addition, Morales (`709) requires certain characteristic XPS features of the pellet exteriors after presulfiding whereas the catalyst of the instant invention requires a specified molybdenum gradient as determined by measuring the molybdenum/aluminum atomic ratios by XPS for the catalyst pellet exteriors and the pellets in a crushed form as measured on the fresh catalysts in an oxide state.
U.S. Pat. No. 4,579,649 (Morales et al.) discloses a catalyst preparation and a catalyst composition useful in the hydroconversion of heavy oils, the catalyst containing a Group VIB element (e.g. molybdenum), a Group VIII element (e.g. nickel) and phosphorus oxide on a porous alumina support. The catalyst has certain characteristic features for the three active components (Mo, Ni and P) when the pellet exteriors are examined in a sulfided state using X-ray photoelectron spectroscopy (XPS). Morales (`649) is distinguished from the instant invention in that its catalyst requires phosphorus whereas the catalyst of the instant invention does not. In addition, Morales (`649) requires certain characteristic XPS features of the pellet exteriors after presulfiding whereas the catalysts of the instant invention require a specified molybdenum gradient as determined by measuring the molybdenum/aluminum atomic ratios by XPS for the catalyst pellet exteriors and the pellets in a crushed form as measured on the fresh catalysts in an oxide state.
U.S. Pat. No. 4,520,128 (Morales et al.) discloses a catalyst preparation and a catalyst composition useful in the hydroconversion of heavy oils, the catalyst containing 5-30 wt. % of a Group VIB element (e.g. molybdenum), 0.1-8.0 wt. % of a Group VIII element (e.g. nickel) and 5-30 wt% of a phosphorus oxide on a porous alumina support. The finished catalysts of Morales (`128) have mean pore diameters of 145 to 154 Angstroms. The catalyst has certain characteristic features for the three active components (Mo, Ni and P) when the pellet exteriors are examined in a sulfided state using X-ray photoelectron spectroscopy (XPS). Morales (`128) is distinguished from the instant invention in that its catalyst requires phosphorus whereas the catalyst of the instant invention does not. Morales (`128) also requires a large mean pore diameter (145 to 154 Angstroms) whereas the catalyst of the instant invention has median pore diameters of 120 to 130 Angstroms. In addition, Morales (`128) requires certain characteristic XPS features of the pellet exteriors after presulfiding whereas the catalysts of the instant invention require a specified molybdem gradient as determined by measuring the molybdenum/aluminum atomic ratios by XPS for the catalyst pellet exteriors and the pellets in a crushed form as measured on the fresh catalysts in an oxide state.